Asked October 05, 2015, 1:51 PM EDT
Washington County Oregon
Judging from your description of millions of tiny white flying insects, it’s likely you are seeing ash whiteflies, Siphoninus phillyreae, which were first identified in Oregon during 2014. Many people in our nearby counties have noticed clouds of the same speck-sized flying insects during the past several weeks. Judging from the number of calls and emails we’ve been receiving from the public, it’s obvious the whiteflies have expanded their territory this year. These whiteflies have been potentially serious pests of ash trees and certain other woody plants elsewhere but, in those areas, are now under good control from introduced natural enemies.
Very little is known at this time about how damaging ash whitefly might be in Oregon or what sort of management may be needed. Treatment, if needed, should only be applied if infested leaves are found because the susceptible targets are the small oval youngsters.
This webpage (late 2015) for commercial growers has some background information and images of infested leaves: http://oregonstate.edu/dept/nurspest/Ash_whitefly.html.
Also see this recent news report: http://oregonstate.edu/dept/nurspest/Ash_whitefly.html